Anonymous visitors are shown a SourceForge login screen when they attempt to view a hosted MediaWiki.
There are known issues with redirects and https links with the Hosted Apps platform. The easiest way to workaround this is to always present the link as an http link.
Also note that we recommend migrating away from the Hosted Apps platform due to the impending Hosted Apps Retirement.
Chris Tsai, SourceForge.net Support
Look at the link. It is an http link. I was aware that https caused trouble so I used http links. Recently I clicked the http link and got a login screen.
I did use that link, and it worked fine, hence my assumption that you were being affected by the known https bug. In any case though, as I mentioned earlier, we are planning to retire the Hosted Apps platform, so we're not going to be fixing any bugs with it.